Bottle-shaped container made of synthetic resin

ABSTRACT

A container has a grounding portion that is free from sink and can prevent sink from occurring, so that it can secure its self-standing ability. The bottle-shaped container made of synthetic resin comprising a neck, a body and a bottom, said bottom including a grounding portion, said bottom being formed at a center thereof with a central bulged section protruding inwardly, said container showing a polygonal transversal cross section, characterized in that a peripheral bottom wall is formed between an outer periphery of the central bulged section and the grounding portion, said peripheral bottom wall forming a step located below the central bulged section and above the grounding portion, and said grounding portion is provided with a recess in a portion formed with an orientation magnification which is smaller than an orientation magnification with which a portion on and along a diagonal line is formed.

BACKGROUND OF THE INVENTION

This invention relates to a bottom structure of a bottle-shapedcontainer made of synthetic resin showing a polygonal transversal crosssection. More particularly, it relates to a bottom structure of abottle-shaped container made of synthetic resin showing a polygonaltransversal cross section, and having a central bulged section formed ata center of the bottom and projecting into the container.

A bottle-shaped containers made of synthetic resin such aspolyethyleneterephthalate is formed by biaxially-oriented blow-molding apreform. Such containers are widely used for the purpose of containingbeverages. The container shows a transversal cross section that may besubstantially circular, substantially square, substantially rectangularor of some other profile. The container is required to have a flatgrounding portion at a bottom thereof so as to be able to stand onitself.

FIGS. 8–10 illustrate a known container 101 of the type underconsideration that has a substantially rectangular transversal crosssection. The container 101 comprises a neck 103, a body 105 and a bottom107 connected to the body 105. The body 105 shows a substantiallyrectangular transversal cross section, and comprises two longer sides151, 152 and two shorter sides 153, 154. The bottom 107 comprises abottom wall 171 having a grounding edge 175 at a peripheral edgethereof, and a bottom peripheral wall 173 standing upwardly from thegrounding edge 175. The bottom wall 171 is formed at a center thereofwith a central bulged section 177 which is protruded into the container.The bottom wall 171 between the central bulged section 177 and thegrounding edge 175 operates as a grounding portion 181. The groundingportion 181 is required to be flat, so that the container can stand onitself.

Meanwhile, in a case of a container showing a substantially circulartransversal cross section, a preform is radially oriented to form thecontainer. Since the preform is substantially uniformly oriented in allradial directions, the grounding portion of the container is uniformlyoriented to be formed in all radial directions.

However, in a case of a container showing a substantially square orrectangular transversal cross section, an orientation magnification ofthe preform on a diagonal line is the largest, and an orientationmagnification at a portion located off the diagonal line is smaller thanthat on the diagonal line. Thus, the portion of the container formedwith such smaller orientation magnification tends to occur sink, so asto effect a moldability and the self-standing ability of the container.

In the case of the prior art container illustrated in FIGS. 8–10, theorientation magnification of the preform is the largest on the diagonalline L. To the contrary, the orientation magnification of the preform isthe smallest on a center line M (passing through a center of each of thelonger sides). As a result, sink tends to occur easily at a portionwhich nucleus is the center line M (shaded portion in FIG. 10), so as toconsequently lose the flatness of the grounding portion and damage theself-standing ability of the container. Additionally, the orientationmagnification of the preform on a center line N (passing through acenter of each of the shorter sides) is smaller than the orientationmagnification on the diagonal line L. Thus, sink tends to occur easilyat a portion which nucleus is the center line N, compared with a portionon the diagonal line L.

SUMMARY OF THE INVENTION

In view of the above identified circumstances, it is therefore theobject of the present invention to prevent sink from occurring, and toprovide a container of the type under consideration in which, even if asink is produced, it does not adversely affect the self-standing abilityof the bottle-shaped container.

According to the invention, the above object is achieved by providing abottle-shaped container made of synthetic resin comprising a neck, abody and a bottom, said bottom including a grounding portion, saidbottom being formed at a center thereof with a central bulged sectionprotruding inwardly, said container showing a polygonal transversalcross section, characterized in that a peripheral bottom wall is formedbetween an outer periphery of the central bulged section and thegrounding portion, said peripheral bottom wall forming a step locatedbelow the central bulged section and above the grounding portion, andsaid grounding portion is provided with a recess in a portion formedwith an orientation magnification which is smaller than an orientationmagnification with which a portion on a diagonal line is formed.

Preferably, said recess has a length in a peripheral direction of thecontainer equal to 20% to 80% of a length of the grounding portion.

If the container shows a substantially rectangular transversal crosssection, the recess is formed at a portion which nucleus is a centerline passing a center of each longer sides. If the container shows asubstantially rectangular transversal cross section, the recess isformed at a portion which nucleus is a center line passing a center ofeach shorter sides.

If the container shows a substantially square transversal cross section,the recess is formed at a portion which nucleus is a center line passinga center of each of opposed sides.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic front view of the first embodiment of a containeraccording to the invention, the container being shown partly in crosssection.

FIG. 2 is a schematic lateral view of the first embodiment of thecontainer according to the invention, the container being shown partlyin cross section.

FIG. 3 is a schematic bottom view of the first embodiment of thecontainer according to the invention.

FIG. 4 is a schematic front view of the first embodiment of theinvention, showing only the bottom thereof.

FIG. 5 is a schematic front view of the second embodiment of a containeraccording to the invention, the container being shown partly in crosssection.

FIG. 6 is a schematic lateral view of the second embodiment of thecontainer according to the invention, the container being shown partlyin cross section.

FIG. 7 is a schematic bottom view of the second embodiment of thecontainer according to the invention.

FIG. 8 is a schematic front view of a prior art container shown partlyin cross section.

FIG. 9 is a schematic lateral view of the prior art container of FIG. 8shown partly in cross section.

FIG. 10 is a schematic bottom view of the prior art container of FIG. 8.

FIG. 11 is a schematic bottom view of the third embodiment of thecontainer.

FIG. 12 is a schematic bottom view of the fourth embodiment of thecontainer.

PREFERRED EMBODIMENTS OF THE INVENTION

Now, the first embodiment of the invention will be described byreferring to FIGS. 1–4 of the accompanying drawings. FIG. 1 shows apartial cross section which passes a center of each of shorter sides.FIG. 2 shows a partial cross section which passes a center of each oflonger sides.

A container 1 is made of synthetic resin such aspolyethyleneterephthalate, and obtained by biaxially orientedblow-molding a preform also made of the same synthetic resin. Thecontainer 1 comprises a neck 3, a body 5, and a bottom 7 connected tothe body 5. The body 5 shows a rectangular transversal cross section,and has longer sides 51, 52 and shorter sides 53, 54. The bottom 7 alsoshows a rectangular transversal cross section as shown in FIG. 3. Eachof the longer sides 51, 52 is formed with a recessed panel 55 at acenter thereof. Each of the recessed panels 55 is formed with fourhorizontally extending recessed ribs 57. Each of the shorter sides 53,54 is formed with four horizontally extending recessed ribs 59 at acenter thereof. However, the present invention is by no means limited tosuch recessed panels 55 and recessed ribs 57, 59.

While the container 1 of the illustrated embodiment shows a rectangulartransversal cross section, a container according to the invention isdefined to have a polygonal transversal cross section (having three ormore corners), and the transversal cross section thereof is not limitedto tetragon. However, a container showing a polygonal transversal crosssection with a smaller number of corners is more advantageous for thepurpose of the present invention, because the cross section comes closerto a circle as number of corners increases. A container according to theinvention is not limited to have a polygonal transversal cross section,and may show a square transversal cross section or some other regularpolygonal transversal cross section.

The bottom 7 includes a bottom wall 71 having a grounding edge 75 at aperipheral edge thereof, and a bottom peripheral wall 73 standingupwardly from the grounding edge 75. The bottom wall 71 is formed at acenter thereof with a bulged or domed section 77 which protrudes intothe container. The central bulged section 77 shows a dome shape as isknown in the art.

A peripheral bottom wall 79 is formed around the central domed section77. The peripheral bottom wall 79 is slightly recessed into thecontainer from the bottom wall 71.

The bottom wall 71 between the peripheral bottom wall 79 and thegrounding edge 75 operates as grounding portion 81 or grounding surfaceof the container. In other words, the peripheral bottom wall 79 isformed between the central domed section 77 and the grounding portion81. The peripheral bottom wall 79 forms a step that is located below thecentral domed section 77 and above the grounding portion 81.

In the grounding portion 81 of the container illustrated in FIGS. 1–3, awidth of the grounding portion 81 is the smallest on a center line M—Mwhich passes a center of each longer sides of the rectangular shape.When forming a container from a preform, an orientation magnification isthe smallest on the center line M—M in the bottom of the container.Thus, sink is most likely to occur on the center line M—M in thegrounding portion 81.

In the embodiment of FIGS. 1–3, the grounding portion 81 is providedwith recesses 85, each of which is concaved into the container, and eachof which is formed at a portion where the center line M—M is nucleus.

As described above, the recess 85 is provided in areas where sink tendsto occur. Thus, even if sink occurs, sink occurs in the recess 85 anddoes not occur in the grounding portion 81, so that the container cansecure its self-standing ability. In addition, due to the recesses 85,the orientation magnification becomes large, so as to consequentlyprevent sink from occurring.

Still additionally, the bottom of the container according to theinvention is highly undulated due to the formation of the peripheralbottom wall 79, so that the bottom is sufficiently oriented. As aresult, sink is prevented from occurring at the bottom. Stilladditionally, the peripheral bottom wall 79 operates as rib, so as toreinforce the bottom. Thus, even if a sink occurs in the groundingportion 81, distortion of the sink is absorbed by the peripheral bottomwall 79, so that the central bulged section 77 is not distorted, andhence the bottle-shaped container shows a neat and well-balancedprofile. Furthermore, if the bottom of the bottle-shaped container isentirely heated in order to heat content stored therein, any thermaldeformation is absorbed by the peripheral bottom wall 79.

In the first embodiment, the recess 85 is formed at the portion whichnucleus is the center line M—M passing the center of each of the longersides of the rectangular shape. However, for the purpose of theinvention, the recess 85 is formed in a direction where the orientationmagnification is smaller than that in a direction of a diagonal.Therefore, the recess 85 may be formed at a portion which nucleus is acenter line N—N passing a center of each of the shorter sides of therectangular shape, as the below-described second embodiment. Both thecontainer of the first embodiment and that of the second embodiment showa rectangular transversal cross section. However, if a container shows aregular polygonal (square) transversal cross section, the recess 85 isformed along a direction where the orientation magnification is smallerthan the orientation magnification along the diagonal. Morespecifically, as illustrated in FIG. l2, the recess is formed at aportion which nucleus is a center line passing a center of each ofopposed sides. While each of the recesses 85 is formed to cover thebottom wall 71 and the bottom peripheral wall 73 in the illustratedembodiments, the recess 85 may be formed only in the bottom wall 71 forthe purpose of the invention.

Each of the recesses 85 has a depth of 0.5–25.0 mm, preferably 0.5–5.0mm. In the illustrated embodiments, each of the recesses 85 has a depthof 2.0 mm. If the depth is smaller than 0.5 mm, sink cannot besufficiently absorbed by the recesses 85. If the depth exceeds 25.0 mm,the effect of absorbing sink is not further improved.

Each of the recesses 85 has a length equal to 20% to 80% of a length ofthe grounding portion. More specifically, referring to FIG. 4, a length“A” of the recess 85 is equal to 20% to 80% of a length “B” of thegrounding portion 81. If the length of the recess 85 is less than 20% ofthat of the grounding portion 81, sink may occur in not only the recess85 but also the grounding portion 81. If the length of the recess 85 ismore than 80% of that of the grounding portion 81, an area of thegrounding portion is too small to affect the self-standing ability ofthe container. Preferably, the length of the recess 85 is 40–50% of thelength of the grounding portion 81.

In the second embodiment illustrated in FIGS. 5–7, the container isprovided with not only the recesses 85 at the portions each of whichnucleus is the center line M—M, but also the recesses 86 at portionseach of which nucleus is the center line N—N passing the center of eachof the shorter sides of the rectangular shape. Because the orientationmagnification on the center line N is smaller than that on the diagonalline L, the portion on and along the center line tends to sink comparedto the portion on the diagonal line L. Thus, the recess 86 is providedat a portion which nucleus is the center line N. Like the recess 85, therecess 86 has a depth between 0.5 and 25.0 mm, and has a length equal to20% to 80% of the length of the grounding portion. Alternatively, asillustrated in FIG. 11, the container is provided with recesses 86formed only at a portion which nucleus is a center line N—N vassing acenter of each of the shorter sides 53, 54 of the rectangular shape, asa third embodiment.

The second embodiment is identical with the first embodiment illustratedin FIGS. 1–3 in terms of configuration and advantages except that it isprovided with recesses 86. Therefore, it will not be described here anyfurther.

Note that FIG. 5 shows a partial cross section which passes the centerof each of shorter sides of the rectangular shape. FIG. 6 shows apartial cross section which passes the center of each of longer sides ofthe rectangular shape.

According to the invention, a peripheral bottom wall is formed tosurround a central bulged section, and a recess is formed at a portionof a bottom, which portion is formed in an orientation magnificationsmaller than an orientation magnification on a diagonal. Therefore, evenif a sink occurs, it will be found only somewhere in the recess and willnot appear in the grounding portion, so that the self-standing abilityof the container will be secured. Additionally, since the recess isprovided, the orientation magnification of a preform becomes large, soas to consequently prevent sink from occurring. Still additionally,since the peripheral bottom wall is provided, the bottom of thecontainer is sufficiently oriented, to consequently prevent sink fromoccurring in the bottom. Still additionally, the peripheral bottom walloperates as rib, so as to reinforce the bottom and prevent the centralbulged section from being distorted.

When the recess has a length which is equal to 20% to 80% of a length ofa grounding portion in a peripheral direction of the container, sink canbe sufficiently absorbed, so that the self-standing ability of thecontainer will be secured.

When the container shows a substantially rectangular or squaretransversal cross section, and when the recess is formed at a portionwhich nucleus is a center line of the bottom, sink will not occur in thegrounding portion, to reliably secure the self-standing ability of thecontainer.

1. A bottle-shaped container mails of synthetic resin comprising: aneck, a body and a bottom, said bottom including a grounding portion,said bottom being formed at a center thereof with a central bulgedsection protruding inwardly, said container showing a polygonaltransversal cross section, wherein a peripheral bottom wall is formedbetween an outer periphery of the central bulged section and thegrounding portion, said peripheral bottom wall forming a step locatedbelow the central bulged section and above the grounding portion, saidgrounding portion is provided with a recess in a portion formed with anorientation magnification which is smaller than an orientationmagnification with which a portion on a diagonal line is formed, and therecess has a depth equal to 0.5 mm to 25.0 mm.
 2. The containeraccording to claim 1, wherein said recess has a length in a peripheraldirection of the container equal to 20% to 80% of a length of thegrounding portion.
 3. The container according to claim 2, wherein thecontainer shows a substantially rectangular transversal cross section,and the recess is formed at a portion which nucleus is a center linepassing a center of each longer sides.
 4. The container according toclaim 2, wherein the container shows a substantially rectangulartransversal cross section, and the recess is formed at a portion whichnucleus is a center line passing a center of each shorter sides.
 5. Thecontainer according to claim 2, wherein the container shows asubstantially square transversal cross section, and the recess is formedat a portion which nucleus is a center line passing a center of each ofopposed sides.
 6. The container according to claim 3, wherein thecontainer shows a substantially rectangular transversal cross section,and the recess is formed at a portion which nucleus is a center linepassing a center of each shorter sides.